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Characteristics Of Vapour Compression Refrigeration Cycles Engineering Essay

This undertaking is a survey on a public presentation of a Vapor Compression Refrigeration System VCRC. The public presentation of this type of infrigidation system is being investigated by utilizing different type of enlargement valves or besides known as restricting valves. I am utilizing three types of valves upon carry oning this survey which are thermostatic enlargement valve, capillary tubing enlargement valve and constant-pressure enlargement valve. Performance of infrigidation systems will be investigated on two sort of environing which are closed and unfastened surrounding. A light bulb will move as a warming burden which will increase the inlet temperature of air on vaporization. This undertaking besides discuss about the ideal application of each type of enlargement valves. Which mean, where, when and what application the three types of enlargement valves should be used for a better consequence.

Refrigeration is the action of chilling, and in patterns this requires remotion of heat and flinging it at higher temperature. Therefore, infrigidation is a scientific discipline of traveling heat from low temperature part to the high temperature part.

Refrigeration can be defined as a procedure of accomplishing and keeping a temperature below that of the milieus, with the purpose to chill some merchandise or infinite to the needed temperature. The most of import applications of infrigidation are the saving of perishable nutrient merchandises. Refrigeration systems besides used for supplying thermic comfort to human existences by utilizing air conditioning. Air Conditioning refers to the intervention of air so as to simultaneously command its temperature, wet content, cleanliness, olfactory property and circulation, as required by residents, a procedure, or merchandises in the infinite. The topic of infrigidation and air conditioning has evolved out of human demand for nutrient and comfort, and its history day of the months back to centuries.

In infrigidation system, heat must be removed from the infinite country specifically the goods or affair we need to chill and released to the environment. Nature of heat motion is, heat ever moves from the hotter to the colder infinite. To reassign heat from hot part to cold part, particular device is required. The device is called Refrigerator. Refrigerator is a cyclic device and it is utilizing a fluid called refrigerant as a working fluid.

As known there are two common methods for infrigidation which are natural and mechanical. In natural infrigidation, ice is used to bring forth a circulation of air around the blocks of ice. Therefore some of the heat from the go arounding air is transferred to the ice therefore chilling the air. This method peculiarly used in air conditioning application. As in mechanical infrigidation, refrigerant is used as a working fluid. Refrigerant is a substance that is capable to reassign heat that it absorbs at low temperatures and force per unit areas to a distilling medium. Refrigerator is an illustration of mechanical infrigidation.

In a icebox, coolant is cooled in a capacitor ; from there it flow to the evaporator, where air is cooled by contact with the spiral.

Figure: Example of Refrigerator [ A©2006 Publications International, Ltd. ]

Types of infrigidation rhythm

Vapor Compression Refrigeration System

Vapor compaction infrigidation system is the most common infrigidation system used today. In vapor compaction infrigidation rhythm ( VCRC ) , there are four major thermic procedure take topographic point which is enlargement, vaporization, compaction and condensation. In all practical applications, the existent VCRC is lower than the ideal rhythm. This caused by several factors such as clash losingss, heat exchanges between parts on the system and force per unit area beads in suction and discharge lines.

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Figure: Single phase VCRC [ The Full wiki/ infrigidation rhythm ]

Based on Figure 2, compaction procedure is done on compressor followed by condensation procedure on capacitor, enlargement procedure on enlargement valve and in conclusion evaporation procedure on evaporator.

Compression Process on Compressor

Low-pressure vapour of refrigerating enters the compressor and so being compressed and moved to condenser as a high-pressure vapour ( superheated ) .

Condensation Process on Condenser

The superheated vapour of refrigerant is so travels through the condenserA which first cools and removes the superheat and so condenses the vapour refrigerant into a liquid refrigerant by taking extra heat at changeless force per unit area and temperature.

Expansion Procedure on enlargement Valve

The liquid refrigerant is so goes through theA enlargement valveA which is besides known as restricting valve where its force per unit area will suddenly diminish, causingA brassy evaporationA and auto-refrigeration of, typically, less than half of the liquid. By undergoing enlargement procedure, mixture of liquid and vapour refrigerant is produced at low temperature and force per unit area.

Evaporation Process on Evaporator

The cold liquid-vapor refrigerant is so travels through the evaporator spiral or tubings and it is wholly vaporized by chilling the warm air ( from the infinite being refrigerated ) and being blown by a fan across the evaporator spiral or tubings. The ensuing refrigerating vapour returns to the compressor recess to finish the thermodynamic rhythm.

Vapor compaction infrigidation system utilizing top-quality energy such as mechanical work. It has more noise and wear is possible to happen in the compressor since traveling parts is placed at that place. Coefficient of public presentation, COP of VCRC will diminish if the force per unit area of the evaporator decreases. Performance of VCRC is adversely affected at partial burden.

Vapor Absorption Refrigeration System

Vapor Absorption Refrigeration SystemA uses a heat beginning such as solar and kerosene-fueled fire to supply the energy needed to drive the chilling system. Vapor soaking up Refrigeration system is a popular option to regularA compressor refrigeratorsA where electricity is undependable, dearly-won, or unavailable, where noise from the compressor is debatable, or where excess heat is available such as from turbine fumes or industrial procedures. Absorption iceboxs powered by heat from theA combustionA ofA liquefied crude oil gasA are frequently used for nutrient storage inA recreational vehicles.

There are two type of vapor soaking up infrigidation system that is single-effect and dual consequence. Single-effect soaking up system is utilizing neither ammonium hydroxide or H2O while double-effect soaking up system uses lithium bromide or H2O.

Since the presence of ammonium hydroxide or Li bromide straight into a confined infinite which is full of human is unsafe, vapor soaking up system which used this stuff should be placed outside the edifice to be cooled. However, vapor soaking up that utilizing ammonium hydroxide or Li bromide is non practical to be used on a edifice since it is impossible to shriek this stuff into the edifice. Therefore all soaking up rhythm equipment is so designed to chill H2O which is so piped into the edifice.

The chilled H2O is piped through to fan coil units in each of the learned infinites. The application of vapour soaking up system utilizing H2O is hence good suited to multiple room systems or big infinites necessitating air conditioning. This is because soaking up hair-raisers are a well-established engineering that can offer considerable advantages over conventional, automatically driven, vapor compaction chillers.A

Absorption rhythm is utilizing a unstable brace instead than utilizing a automatically driven or an electrically powered compressor to be map. The soaking up chilling rhythm is driven by the heat beginning, such as gas burner, steam or hot H2O. This heat beginning is used to boil and drive the refrigerant out of the refrigerant/absorbent mixture. This mixture is usually termed solution.A

The refrigerant is so traveling through a capacitor to take the latent heat of condensation, therefore returning the refrigerant into liquid signifier. The refrigerant is so passed to the evaporator where vaporization procedure draws heat from the recirculating chilled H2O. The ensuing vapour from the evaporator is attracted and absorbed by the absorptive solution to finish the rhythm. In consequence, the mechanical compressor of a conventional vapor compaction rhythm has been substituted with a ‘chemical pump ‘ driven by heat.

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Figure: Single Effect Absorption Cooling [ ACR News ]

Steam Jet Refrigeration system

Steam Jet Refrigeration system is utilizing the rule of liquids blinking under vacuity in a chamber. If the flash vapour removed from the chamber, the liquid will chill to the needed temperature. In pattern, more than one chilling phase is normally present. Steam Jet Refrigeration system will go more economical when both steam and chilling H2O is readily available. Steam jet infrigidation system working start with the steam passed through aA vacuity ejectorA of high efficiency to wash up a separate, closed vas which forms portion of a cooling H2O circuit. The partial vacuity in the vas causes some of the H2O to vaporize, therefore giving up heat throughA evaporative chilling. The chilled H2O is pumped through the circuit to air ice chests, while the evaporated H2O from the ouster is recovered in separateA condensersA and returned to the chilling circuit.

InA steam jet infrigidation systems, H2O can be used as the refrigerant. Water is absolutely safe for human. These sorts of systems were applied successfully to infrigidation in the early old ages of century. At low temperatures the impregnation force per unit areas are low ( 0.008129 saloon at 4A°C ) and the specific volumes are high ( 157.3 m3/kg at 4A°C ) . The temperatures that can be attained utilizing H2O as a refrigerant are non low plenty for most infrigidation applications but are in the scope which may fulfill air conditioning, chilling, or chilling demands. These systems besides used in some chemical industries for several procedures, such as the remotion of paraffin wax from lubricating oils. The application of steam jet infrigidation system besides including chilling a hot caustic liquid expeditiously to any coveted temperature and the chilling of fruit juices instantaneously.Note that a steam jet infrigidation system is non suited to be used when the needed temperatures are below 5A°C.

Steam jet infrigidation systems use steam ousters to cut down the force per unit area in a armored combat vehicle incorporating the return H2O from a chilled H2O system. The steam jet ouster utilizes the energy of a fast-moving jet of steam to capture the flash armored combat vehicle vapour and compress it. Flashing a part of the H2O in the armored combat vehicle reduces the liquid temperature. Hard-hitting steam expands while fluxing through the nozzle 1. The enlargement causes a bead in force per unit area and an tremendous addition in speed. Due to the high speed, brassy vapour from the armored combat vehicle is drawn into the fleetly traveling steam and the mixture enters the diffusor. The speed is bit by bit reduced in the diffusor but the force per unit area of the steam at the capacitor is increased 5-10 times more than that at the entryway of the diffusor ( e.g. from 0.01 saloon to 0.07 saloon ) .

The chief advantages of this system are the use of largely low-grade energy and comparatively little sums of shaft work. Using Steam Jet infrigidation system will necessitate negligible care and a works can be fabricated in any suited stuff of building. In steam jet infrigidation system, there is no traveling portion involved.

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Figure: Steam Jet Refrigeration System [ Sirindhorn International Institute of Technology, Thammasat University ]

Thermoelectric Refrigeration System

An consequence of infrigidation can besides be achieved without utilizing any traveling parts. This is done by merely go throughing a little current through a closed circuit which is made up from two dissimilar metals. This type of consequence is called the Peltier consequence, and a icebox which is works utilizing this sort of rule is called a thermoelectric icebox.

The thermoelectric device is like the conventional thermocouple. It is utilizing two dissimilar stuffs as a medium to reassign heat from one another. In a thermoelectric icebox, there are two junction between the two different metals used. One junction is placed in the refrigerated infinite and the other one is placed in the ambient environing. The temperature of the junction which is located in the refrigerated infinite will diminish when the current passed through and make a possible difference. An opposite consequence will happen on the other junction.

Under steady-state operating conditions, heat is transferred from the refrigerated infinite to the cold junction. The other junction will be at a temperature above the ambient, and heat will be transferred from the junction to the milieus.

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Figure: Thermoelectric Refrigeration Effect

The thermoelectric infrigidation consequence are excessively expensive for a normal domestic and commercial applications which are run merely on utilizing a regular family current. This construct usually suited to recreational applications due to the weight of thermoelectric icebox which is light, compact and it is besides insensitive to gesture or tilting. This type of icebox besides has no traveling parts, and can run straight from 12-volt batteries.

Using thermoelectric icebox will give a advantages to the nutrient and drinks. It will maintain the nutrient and drinks cold and dry. There besides no otiose infinite for ice. The advantages of thermoelectric infrigidation system include ;

Compact size

Very small infinite is required by the chilling system.

Lightweight

Can be carried with one manus

Cheap

Use Low Battery to be map.

Comparison between infrigidation system

A

Feature

Refrigeration System

Compaction

Absorption

Steam Jet

Principle of chilling

Zaping a Refrigerant

Zaping an Ammonia gas

Beginning of Energy

Mechanical work

Heat

Concentration

Weight

Portability

Heavy

Must be kept degree within 2-3 grades

Monetary value

Battery Drain

Draw more current when running

6.5-7.5 A

Cooling Performance

Most efficient in hot conditions

Less efficient at high ambient

Freezing Ice regular hexahedrons in hot conditions

excellent

Not practical

Safety

Leaking of refrigerant

Leaking of refrigerant

Dependability

Exposed to have on

and may necessitate adept serving from clip to clip

Service & A ; Maintenance

Required trained mechanics and particular service equipment

Components on Vapor Compression Refrigeration Cycle

Vapour compaction infrigidation system consist of several mechanical constituents that helps the systems to be map. Four major constituents on vapour compaction infrigidation system include compressor, capacitor, enlargement valve and evaporator.

In choice of any constituents on infrigidation system, there are many factors that we need to see really carefully, that is:

Keeping entire infrigidation handiness while the burden varies from 0 % to 100 %

Frost control for uninterrupted public presentation application.

Variation in affinity of oil for refrigerant caused by big temperature alterations, and oil migration outside the compressor crankcase.

Choice of chilling medium.

Direct enlargement refrigerant

Gravity or pump recirculated or flooded refrigerant.

Secondary coolan ( e.g. seawaters, salts and ethanediol )

System efficiency and maintainability

Type of capacitor

Air

Water

Evaporatively cooled

Design of the compressor

Open

Hermetic

Semihermetic motor thrust

Reciprocating

Prison guard

Rotary

Type of system

Single phase

Single economized

Compound or cascade agreement

Choice of refrigerant.

Type of refrigerating fundamentally chosen based on operating temperature and force per unit area.

Compressor

Compressor is one of the major constituents on infrigidation system. There are two chief maps of compressors in the infrigidation rhythm. The first 1 is to pump the refrigerating vapor from the evaporator so that the coveted temperature and force per unit area can be maintained in the evaporator. The 2nd map is to increase the force per unit area of the refrigerating vapor through the procedure of compaction, and at the same time increase the temperature of the refrigerating vapor. Therefore the force per unit area will alter and do the superheated refrigerant flows through the systems.

Compressor besides known as the bosom of the vapour compaction infrigidation system because it is supplied energies to run the system. Compressor can be divided into two chief classs which are displacement compressors and kineticss compressors. Both supplanting and kineticss compressors can be hermetic, semi hermetic or unfastened types. Both compressors besides pumps refrigerant throughout the systems and produce significant addition in the force per unit area of the refrigerant.

Supplanting Compressors

These types of compressors used a shaft work to increase the refrigerating force per unit area by cut downing the compaction volume in the chamber. Reciprocating compressors, vane ( rotary ) compressors and coiling traffic circle ( coil ) compressors are including in a group of supplanting compressors.

Reciprocating compressors compress the refrigerant gas merely on frontward shot. A Piston is build to be individual moving in a big capacity scope up to 100s of kW.

Capacitor

Expansion Valve

Evaporator

Refrigeration Cycle

Expansion valve choice

Thermostatic Expansion valve

Capillary Tube Expansion valve

Constant-pressure Expansion valve

Refrigerant

Types of refrigerant

Features of refrigerants

Choice of refrigerant

Performance of Vapor Compression Refrigeration Cycle

Chapter 2

LITERATURE REVIEW

Chapter 3

EXPERIMENTAL METHODOLOGY

Introduction

Background of Study

Parameters Involved

Equipments and Apparatus set up

Standard Operating Procedure

Chapter 5: Consequence AND DISCUSSIONS

Chapter 6: Decision AND RECOMMENDATIONS

REFFERENCES

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